1. Field of the Invention
The present invention relates to a method of manufacturing a fiber-optic collimator for use in coupling two optical fibers together at a minimized loss.
2. Description of the Prior Art
To manufacture the fiber-optic collimator, the following three methods have generally been well known in the art.
(1) A lens holder and a fiber sleeve forming a second fiber-optic collimator is held in abutment with a first fiber-optic collimator, which has been optically adjusted on a generally V-shaped groove, and both are then fixed in position after the distance z between the lens holder and the fiber sleeve has been adjusted to minimize the coupling loss.
(2) A lens holder and a fiber sleeve forming a second fiber-optic collimator mounted on a slide adjustment is held in position so as to confront a first fiber-optic collimator which has been adjusted, and both are then fixed in position after the relative positional relationship (Axis offset: x, y; Spacing: z; and Axis tilt: .theta., .phi.) between the lens holder and the fiber sleeve and, also, the relationship in position (X, Y, .THETA., .PHI.) between the lens holder and the first fiber-optic collimator have been adjusted.
(3) While a lens holder and a fiber sleeve arranged in series with each other is oriented towards a screen and a light spot formed on the screen by a beam having passed through a fiber-optic collimator fixed on the lens holder is viewed from front or rear of the screen by a photographic camera, the distance z between the lens holder and the fiber sleeve is adjusted to render the diameter of the light spot to attain a minimum value and both are then fixed.
However, it has been found that any one of the foregoing prior art methods (1) to (3) have problems which will now be discussed.
According to the first-mentioned prior art method (1), the freedom of adjustment available is limited to the distance z between the lens holder and the fiber sleeve and, therefore, it is not possible to provide a low-loss fiber-optic collimator utilizing a single mode optical fiber which requires a coupling loss of, for example, not greater than 0.05 dB.
According to the second-mentioned prior art method (2), the freedom of adjustment available is limited to 5 axes and, therefore, a precise adjustment should be accomplished. However, since 4 axes are required to accomplish the adjustment in position of the first fiber-optic collimator, it is extremely difficult to locate an optimum position.
With respect to the last-mentioned prior art method (3), since a change in spot diameter of the beam on the screen is very small as compared with a change in distance between the lens holder and the fiber sleeve, not only is a strict adjustment difficult, but also the relative positional relationship between the lens holder and the fiber sleeve is not possible at all.